Amphibious vehicles have a flattened vehicle bottom surface and a shortened length in a front-rear direction of the vehicle body in order to improve the running performance across rough terrain on land. Such amphibious vehicles cause the vehicle body to tilt backward due to waves created by a bow of the vehicle body during traveling on water. This increases the fluid resistance due to water applied to the vehicle body during traveling on water. Therefore, there is proposed an amphibious vehicle including a rear flap having one end fixed to a lower end portion of a structural plane of the vehicle body and extending to a rear side of the vehicle (see Patent Document 1).
The rear flap of the amphibious vehicle described in Patent Document 1 is mounted in a vertically rotatable manner via a hinge disposed at a lower part of a rear surface of the vehicle body, and is mounted at a predetermined angle with respect to the rear surface of the vehicle body, via an extendable and contractible support member which has one end fixed to a lower part of the vehicle body and the other end attached to the rear flap. The rear flap has substantially the same width as that of the vehicle body.
Accordingly, during traveling of the amphibious vehicle on water, since waves in water pass through rearward from a lower surface of the vehicle body via a lower surface of the rear flap, lift is applied from a lower side to an upper side of the rear surface of the vehicle body, and it is possible to decrease wave drag from a front surface of the vehicle body.